Plugin for getting DPDK ports link status and keep alive events.

Dpdkevents plugin collects and reports following events from DPDK based
applications:
- link status of network ports bound with DPDK
- keep alive events related to DPDK logical cores

In order to get link status plugin forks child process that attaches itself to
DPDK application as secondary DPDK process and fetches link status data using
DPDK API. This is the same approach like for dpdkstat plugin, also the same
utils_dpdk.c helper is utilized.

For getting keep alive events plugin communicates with DPDK application
via shared memory area. This is possible only if keep alive feature
is implemented in monitored application.
More details can be found under link
http://dpdk.org/doc/guides/sample_app_ug/keep_alive.html

Minimal required version of DPDK is 16.07.

Change-Id: Id820407ea933b1ecc31a72b6e344a6ec186ec780
Signed-off-by: Krzysztof Matczak <krzysztofx.matczak@intel.com>